JP5619398B2 - Heat-sensitive recording developer composition and heat-sensitive recording material containing the heat-sensitive recording developer composition - Google Patents

Description

  The present invention relates to a heat-sensitive recording developer composition comprising a diphenylsulfone cross-linking compound and a heat-sensitive recording material containing the heat-sensitive recording developer composition. More specifically, the present invention relates to an image portion and an uncolored color. The present invention relates to a heat-sensitive recording material having excellent storage stability.

  A heat-sensitive recording material generally comprises a support on which a heat-sensitive color-developing layer mainly comprising an electron-donating colorless or light-colored dye precursor and an electron-accepting developer is provided. By heating with a laser beam or the like, the dye precursor and the developer react instantaneously and recording occurs. Such a heat-sensitive recording material has been developed for a long time.For example, it is usually colorless, but as a composition that develops color by heating or infrared irradiation, a lactone, lactam, or sultone type non-colored dye base is used. Furthermore, heat-sensitive copying sheets coated with organic acids and heat-fusible substances (Patent Document 1), and phenolic substances that are solid at room temperature react with lactones when liquefied or vaporized at thermographic temperatures, resulting in recording. A heat-sensitive recording material (Patent Document 2) is proposed.

  Such heat-sensitive recording materials have advantages such that recording can be obtained with a relatively simple device, maintenance is easy, noise generation is low, thermal printers such as various portable terminals, ultrasonic echoes, etc. It is used for medical image printers, thermopen recorders such as electrocardiograms and analytical instruments, air tickets, boarding tickets, and POS labels for products.

  Thermosensitive recording materials are required to have various characteristics such as excellent color developability, high color density with low heat, excellent preservation of the resulting image, and whiteness of the uncolored areas. Is done. In particular, for microwave processed food labels, parking tickets, delivery labels, tickets, etc., the reliability of the recorded image is particularly important, and storage stability such as plasticizer resistance, moist heat resistance, heat resistance, etc. is required. Various compounds have been studied for storage stability as a developer.

  For example, α, α′-bis [4- (p-) is a developer that provides a heat-sensitive recording material that is highly sensitive and has little background fogging, and can provide a recording image having excellent storage stability, particularly water resistance and plasticizer resistance. Hydroxyphenylsulfonyl) phenoxy] -p-xylene, α, α′-bis [4- (p-hydroxyphenylsulfonyl) phenoxy] -m-xylene or α, α′-bis [4- (p-hydroxyphenylsulfonyl) A heat-sensitive recording material containing phenoxy] -o-xylene has been proposed (Patent Document 3). In addition, as the developer of thermosensitive recording materials with excellent storage stability of color images, especially plasticizer resistance, oil resistance, light resistance, and heat and humidity resistance, dihydroxydiphenyl sulfone and alkylene dichloride, α, α'-dichloroxylene, etc. A diphenylsulfone cross-linking compound that is a reaction product with the above is exemplified (Patent Document 4). However, these compounds have insufficient heat resistance at the uncolored portion, and it cannot be said that the requirement for high storage stability of the developer is sufficiently satisfied. The present inventor has proposed dihydroxydiphenyl sulfone and 4,4′-bis having an equimolar or less relative to dihydroxydiphenyl sulfone as a color developing material for heat-sensitive recording having excellent storage stability of the image area, in particular heat and heat resistance and oil resistance. Proposed to use diphenylsulfone cross-linked compound that is a polycondensation reaction product with (halomethyl) biphenyl (Patent Document 5), but development of a color developer having further excellent effects on water resistance and moist heat resistance is required. It was.

Japanese Patent Publication No.43-4160 Japanese Examined Patent Publication No. 45-14039 JP-A-7-149713 Japanese Patent Laid-Open No. 10-29969 JP 2008-280283 A

  The present invention provides a developer composition capable of obtaining a heat-sensitive recording material excellent in storage stability of an image area, particularly water resistance and heat and heat resistance, and further excellent in storage stability of an uncolored area, particularly heat resistance, and the developer. The invention was made for the purpose of providing a heat-sensitive recording material containing a colorant composition.

  As a result of repeated studies to solve the above-mentioned problems, the inventors of the present invention have produced a polycondensation reaction between dihydroxydiphenyl sulfone and 4,4′-bis (halomethyl) biphenyl which are useful as a developer composition for thermal recording. The product includes a diphenylsulfone bridged compound (a) represented by the following general formula (1), a diphenylsulfone bridged compound (b) represented by the following general formula (2), unreacted dihydroxydiphenylsulfone, Of these, the diphenylsulfone cross-linking compound (b) is found to be a causative substance that deteriorates the water resistance and heat-and-moisture resistance of the image area and lowers the image density. It came to be completed.

すなわち、本発明は、
［１］下記一般式（１）で表されるジフェニルスルホン架橋型化合物（ａ）を含有する感熱記録用顕色剤組成物であって、下記一般式（２）で表されるジフェニルスルホン架橋型化合物（ｂ）の含有量が３質量％以下であることを特徴とする感熱記録用顕色剤組成物、

［２］上記[１]項に記載の感熱記録用顕色剤組成物と、発色物質として無色又は淡色のロイコ染料とを含有する感熱発色層を支持体上に設けてなることを特徴とする感熱記録材料、
を提供するものである。

That is, the present invention
[1] A developer composition for thermal recording containing a diphenylsulfone crosslinkable compound (a) represented by the following general formula (1), wherein the diphenylsulfone crosslinkable type is represented by the following general formula (2) A developer composition for thermal recording, wherein the content of the compound (b) is 3% by mass or less;

[2] A heat-sensitive color developing layer comprising the heat-sensitive recording developer composition described in [1] above and a colorless or light-colored leuco dye as a color developing material is provided on a support. Thermal recording material,
Is to provide.

  According to the present invention, it is possible to provide a developer composition for thermal recording which is excellent in storage stability of an image area, in particular, water resistance and heat and moisture resistance, and further excellent in storage stability of an uncolored area, particularly in heat resistance. Furthermore, it is possible to provide a heat sensitive recording material using the developer composition for heat sensitive recording.

First, the developer composition for thermal recording of the present invention (hereinafter, sometimes simply referred to as “developer composition”) will be described.
[Developer composition]
The developer composition of the present invention is a developer composition for thermal recording containing a diphenylsulfone crosslinkable compound (a) represented by the following general formula (1), and is represented by the following general formula (2): The content of the diphenylsulfone cross-linking compound (b) represented is 3% by mass or less.

本発明の顕色剤組成物は、ジフェニルスルホン架橋型化合物（ａ）、副生成物であるジフェニルスルホン架橋型化合物（ｂ）、及び未反応のジヒドロキシジフェニルスルホンの混合物を含む。上記ジフェニルスルホン架橋型化合物（ｂ）の含有量は、高速液体クロマトグラフィー（ＨＰＬＣ）で測定することができる。
このような成分を含む本発明の顕色剤組成物は、ジヒドロキシジフェニルスルホンと、４,４'−ビス(ハロメチル)ビフェニルとの反応により得ることができる。
なお、ジフェニルスルホン架橋型化合物（ｂ）は、ジヒドロキシジフェニルスルホンと４,４'−ビス(ハロメチル)ビフェニルとの等モル反応物のメチレンハライド基が加水分解することにより生成したものと考えられる。

The developer composition of the present invention comprises a mixture of diphenylsulfone crosslinkable compound (a), diphenylsulfone crosslinkable compound (b) as a by-product, and unreacted dihydroxydiphenylsulfone. The content of the diphenylsulfone crosslinking compound (b) can be measured by high performance liquid chromatography (HPLC).
The developer composition of the present invention containing such components can be obtained by reacting dihydroxydiphenylsulfone with 4,4′-bis (halomethyl) biphenyl.
The diphenylsulfone bridged compound (b) is considered to be produced by hydrolysis of the methylene halide group of the equimolar reaction product of dihydroxydiphenylsulfone and 4,4′-bis (halomethyl) biphenyl.

  In order for the developer composition of the present invention to have excellent water resistance and moist heat resistance, the content of the diphenylsulfone cross-linking compound (b) which is a causative substance of water resistance and moist heat resistance deterioration is 3 masses. % Or less. In the heat-sensitive recording material using the developer composition in which the content of the diphenylsulfone crosslinking compound (b) exceeds 3% by mass, the water resistance and moist heat resistance of the image area are insufficient, and the density of the image area is reduced. Arise. Although the details of this mechanism of action are unknown, the diphenylsulfone cross-linked compound (b) having an alcoholic hydroxyl group is more compatible with water than the diphenyl sulfone cross-linked compound (a) having both phenolic hydroxyl groups at the end groups. It is considered that the water- and heat-and-moisture resistance of the thermosensitive thermal recording material is weakened and the density of the image area is lowered by containing the diphenylsulfone cross-linking compound (b) because it is highly soluble and easily dissolved in water. In general formula (2), n is an integer of 1 or 2. Since the diphenylsulfone cross-linking compound (b) having n of 3 or more has low water solubility, even if it is mixed in the developer composition, the influence on the water resistance and heat-and-moisture resistance of the image area can be ignored. .

(Diphenylsulfone cross-linking compound)
The diphenylsulfone crosslinking compound in the developer composition of the present invention comprises dihydroxydiphenylsulfone and 4,4′-bis (halomethyl) biphenyl (chloromethyl or bromomethyl is preferred as halomethyl), solvent and basic It can be produced by dehydrohalogenation reaction in the presence of a substance. The reaction temperature is preferably 50 ° C. or higher and the solvent reflux temperature or lower. Examples of the dihydroxydiphenyl sulfone used include 4,4′-dihydroxydiphenyl sulfone, 2,4′-dihydroxydiphenyl sulfone, 2,2′-dihydroxydiphenyl sulfone, and mixtures thereof. Among these, 4,4′-dihydroxydiphenylsulfone is particularly preferably used because it has excellent storability in the image area and can provide a developer composition having heat resistance in the uncolored area. it can.

  Examples of basic substances that can be used in the reaction system include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, triethylamine, and pyridine. These may be used individually by 1 type and may be used in combination of 2 or more type. The amount of the basic substance to be used must be appropriately selected because the polymerization mode varies depending on the reaction solvent to be used, but it is preferably 2.0 to 3.0 moles of 4,4′-bis (halomethyl) biphenyl. It is more preferable that it is 2.1-2.6 mol times. If the amount of basic substance used is less than the above, the reaction rate may decrease. On the other hand, even if a basic substance exceeding the upper limit is used, the reactivity does not change, and the by-product amount of the diphenylsulfone crosslinked compound (b) may increase.

  Examples of the solvent used in the reaction system include alcohols such as methanol, ethanol, propanol, isopropanol, butanol, and isobutanol; glycols such as ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol; monoalkyl ethers of glycols; Dialkyl ethers of glycols; Ketones such as acetone and methyl ethyl ketone; Nitriles such as acetonitrile; Ethers such as tetrahydrofuran; Esters such as methyl acetate, dimethyl carbonate and propylene carbonate; N-methylformamide, N, N-dimethyl Amides such as formamide; Sulfoxides such as dimethyl sulfoxide; Aromatic hydrocarbons such as toluene, xylene and mesitylene; and mixed solvents thereof Doo is possible, furthermore, it is also possible to use a mixed solvent of water and alcohol mixed solvent or a mixture of water and aromatic hydrocarbons. As alcohol used as a mixed solvent with water, isopropanol, ethanol, and methanol are preferable, and isopropanol is particularly preferable. When a mixed solvent of water and alcohols is used, the alcohol is distilled off after completion of the polymerization reaction, and the crystals are separated by filtration to neutralize a hydrogen halide basic substance produced by the reaction, such as sodium chloride. Etc. can be dissolved in water and can be efficiently separated from the reaction product. When the developer composition of the present invention contains a metal ion such as sodium or potassium in an amount exceeding 1000 mass ppm, the water resistance of the heat-sensitive recording material using the compound is lowered or the heat-sensitive recording material is printed. In some cases, the head may be worn out, and management of the metal content is important.

  In the production of the diphenylsulfone bridged compound, the molar ratio of dihydroxydiphenylsulfone to 4,4′-bis (halomethyl) biphenyl was, for example, a solvent in which the reaction product was dissolved, such as N, N-dimethylformamide. The case of using a mixed solvent of water and alcohols differs depending on the polymerization mode, and therefore needs to be selected appropriately. When a mixed solvent of water and alcohol is used, the reaction molar ratio is preferably 10: 2 to 10: 6. By using a mixed solvent of water and alcohols, the solubility of the diphenylsulfone bridged compound (a) represented by the general formula (1) decreases, and the larger the value of m, the easier it is to precipitate, so m = 3 The above polymerization reaction proceeds particularly slowly, and a diphenylsulfone crosslinked compound (a) having m of 6 or less can be obtained efficiently. When the amount of 4,4′-bis (halomethyl) biphenyl relative to dihydroxydiphenylsulfone is less than the lower limit, the amount of unreacted dihydroxydiphenylsulfone in the reaction mixture may increase. If the amount of 4,4′-bis (halomethyl) biphenyl with respect to dihydroxydiphenylsulfone exceeds the upper limit, the amount of diphenylsulfone bridged compound (b) in the reaction product may be increased, which is not preferable. .

  Since the diphenylsulfone cross-linking compound (b) is generated by hydrolysis of the methylene halide group, there is a possibility that the diphenyl sulfone cross-linking compound (b) is produced by using a mixed solvent of water and alcohols. However, by using a mixed solvent of water and alcohol, the reaction product and the hydrogen halide neutralized salt such as sodium chloride can be separated efficiently, and further, diphenyl having m of 6 or less in the general formula (1). It becomes possible to obtain the sulfone-crosslinking compound (a) efficiently. Therefore, if the polycondensation reaction is carried out in a mixed solvent of water and alcohol and the content of the diphenylsulfone cross-linking compound (b) in the reaction product is 3% by mass or less, the thermal recording of the present invention is performed as it is. When the diphenylsulfone cross-linking compound (b) produced by hydrolysis exceeds 3% by mass of the reaction product, the method of removing it by washing is a diphenyl sulfone cross-linking type. This is effective as a method for efficiently obtaining a developer composition containing the compound (a) and having a diphenylsulfone crosslinking compound (b) content of 3% by mass or less.

The developer composition in which the content of the diphenylsulfone crosslinkable compound (b) exceeds 3% by mass dissolves the diphenylsulfone crosslinkable compound (b) and does not dissolve the diphenylsulfone crosslinkable compound (a). By refine | purifying using the organic solvent which does not melt | dissolve, it can be set as the developer composition whose content of a diphenyl sulfone bridge | crosslinking type compound (b) is 3 mass% or less.
Examples of the organic solvent used for such purposes include branched or straight chain alcohols having 1 to 4 carbon atoms such as methanol, ethanol, propanol, isopropanol, butanol, isobutanol, and t-butanol. These organic solvents can be used alone or in combination of two or more. Among these, methanol, ethanol, and isopropanol can be preferably used because they selectively dissolve the diphenylsulfone crosslinking compound (b).

  The amount of the organic solvent used is preferably 3 to 10 times the mass ratio of the developer composition. If the amount of the organic solvent is less than the lower limit, the slurry viscosity becomes too high, which may hinder filtration and washing, and the diphenylsulfone crosslinked compound (b) may not be sufficiently removed. On the other hand, even if an organic solvent is added exceeding the upper limit, the cleaning effect is not changed, and the economy may be impaired. The developer composition having a diphenylsulfone crosslinkable compound (b) content of 3% by mass or less is compared with the developer composition having a diphenylsulfone crosslinkable compound (b) content exceeding 3% by mass. Of organic solvent, preferably heated to 60 ° C. to reflux temperature, mixed and then cooled to about 25 ° C. to 40 ° C., filtered, and if necessary, further filtered residue using the solvent. After washing, it can be obtained by drying, and this operation can be repeated as necessary. If the heating temperature at the time of washing is less than 60 ° C., the diphenyl sulfone cross-linking compound (b) may not be sufficiently dissolved in the organic solvent, and if the filtration temperature is lowered to less than 25 ° C., the diphenyl sulfone cross-linking type dissolved in the organic solvent. There is a possibility that the compound (b) reprecipitates and cannot be separated. The said refinement | purification operation is implemented with respect to the developer composition whose content of a diphenyl sulfone bridge | crosslinking type compound (b) is 3 mass% or less, and the purity of the diphenyl sulfone bridge | crosslinking type compound (a) in a developer composition Can also be increased.

Next, the heat-sensitive recording material of the present invention will be described.
[Thermal recording material]
The heat-sensitive recording material of the present invention comprises a developer composition for heat-sensitive recording of the present invention in which the content of the diphenylsulfone cross-linking compound (b) is 3% by mass or less, and a color-forming substance comprising a colorless or light leuco dye. A heat-sensitive color-developing layer containing is provided on a support.

(Coloring substance)
In the present invention, there is no particular limitation on the colorless or light leuco dye used as the color developing material contained in the thermosensitive coloring layer, and examples thereof include fluorane derivatives, quinazoline derivatives, phthalide derivatives, triphenylmethane derivatives, phenothiazine derivatives, and the like. . Among these leuco dyes, fluorane derivatives are particularly suitable because they have good color developability.

Examples of leuco dyes that are fluorane derivatives include 3-diethylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (2 ′, 4′-dimethylanilino) fluorane, 3 -Diethylamino-6-methyl-7-chlorofluorane, 3-dibutylamino-6-methyl-7-anilinofluorane, 3-diamilamino-6-methyl-7-anilinofluorane, 3- (N-methyl) -N-propyl) amino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-butyl) amino-6-methyl-7-anilinofluorane, 3- (N-methyl-N -Amyl) amino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-pro L) Amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-amyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isoamyl) Amino-6-methyl-7-anilinofluorane, 3- [N-ethyl-N- (4-methylphenyl)] amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N -Cyclohexyl) amino-6-methyl-7-anilinofluorane, 3- (N-pentyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane, 3- (N-hexyl-N-isoamyl) Amino-6-methyl-7-anilinofluorane, 3-diethyl-N-butylamino-7- (2′-fluoroanilino) fluorane, 3- (N-methyl-N-cyclohexyl) amino-6 Chlorofluorane, 3-pyrodyryl 7-dibenzylaminofluorane, 3-bis (diphenylamino) fluorane, 3-diethylamino-6-chloro-7-anilinofluorane, 3-diethylamino-7- (2′-chloroanilino) fluorane, 3-dibutylamino -7- (2'-chloroanilino) fluorane, 3-diethylamino-7-chlorofluorane, 3-butylamino-7- (2'-chloroanilino) fluorane, 3-diethylamino-6-ethoxyethyl-7-anilinofluor Examples thereof include uranium and 3-diethylamino-7-dibenzylaminofluorane.
These leuco dyes may be used singly or in combination of two or more. The amount of the color developing substance to be contained in the thermosensitive color-developing layer is appropriately determined according to the characteristics of the target thermosensitive recording material. You can choose.

(Developer)
In the present invention, a diphenylsulfone crosslinking compound having a diphenylsulfone crosslinking compound (b) content of 3% by mass or less is used as a developer composition, and a conventionally known developer is used in combination. You can also. By combining the developer composition of the present invention with a conventionally known developer, the storability of the image area and the storability of the undeveloped area are further improved without impairing the color developability of the known developer. It becomes possible to make it.

  There are no particular limitations on the developer that can be used in combination, for example, α-naphthol, β-naphthol, 4-octylphenol, pt-octylphenol, pt-butylphenol, p-phenylphenol, 1,1-bis (4- Hydroxyphenyl) -1-phenylethane, 1,1-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (3-methyl-4-hydroxyphenyl) Propane, 2,2-bis (3-phenyl-4-hydroxyphenyl) propane, 2,2-bis (3,4-dihydroxyphenyl) propane, 2,2-bis (2,5-dipromo-4-hydroxyphenyl) Propane, 2,2-bis (3-tert-butyl-4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyphenyl) butane, 2,2-bis (4-hydride) Xylphenyl) methylpentane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) ) Butane, 1,6-bis (4-hydroxybenzoyloxymethyl) hexane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 1,1-bis (4-hydroxyphenyl) -1-phenylethane, bis ( 2-hydroxy-4-chlorophenyl) methane, bis (4-hydroxyphenyl) methane, 1,3-bis (4-hydroxycumyl) benzene, 1,4-bis (4-hydroxycumyl) benzene, 1,4 -Bis (4'-hydroxybenzoyloxymethyl) benzene, 1,4-bis (4-hydroxybenzoyloxymethyl) cyclohexane, 1,3-bis (3'-hydroxybenzoyloxy) Cymethyl) cyclohexane, 1,2-bis (2′-hydroxybenzoyloxy) cyclohexane, α, α-bis (4-hydroxyphenyl) -α-methyltoluene, 4,4′-thiobisphenol, 4,4′-thiobis (2-methylphenol), 4,4′-thiobis (2-chlorophenol), 4,4′-thiobis (6-tert-butyl-2-methylphenol), 1,7-bis (4-hydroxyphenylthio) ) -3,5-dioxahebutane, 1,5-bis (4-hydroxyphenylthio) -3-oxapentane, 1,3-bis (4-hydroxyphenylthio) -2-hydroxypropane, 4,4′-di Phenol sulfoxide, 4,4′-dihydroxydiphenylsulfone, 2,4′-dihydroxydiphenylsulfone, 3,3′-diallyl-4,4′-dihydroxydiphenylsulfone, 4-allylthiol Si-4′-hydroxydiphenylsulfone, 4-benzyloxy-4′-hydroxydiphenylsulfone, 4-isopropoxy-4′-hydroxydiphenylsulfone, 4-ethoxy-4′-hydroxydiphenylsulfone, 4-propoxy-4 ′ -Hydroxydiphenylsulfone, 4-methyl-4'-hydroxydiphenylsulfone, 4-methyl-3 ', 4'-dihydroxydiphenylsulfone, bis-2,4 (phenylsulfonyl) phenol, 4,4'-dihydroxydiphenylsulfonediethyl Ether condensate, 4,4′-bis [(4-methyl-3-phenoxycarbonylaminophenyl) ureido] diphenylsulfone, N- (p-toluenesulfonyl) -N ′-(3-p-toluenesulfonyloxyphenyl) Urea, N- (4′-hydroxyphenylthio) acetyl- -Hydroxyaniline, N- (4'-hydroxyphenylthio) acetyl-4-hydroxyaniline, methyl bis (4-hydroxyphenyl) acetate, butyl bis (4-hydroxyphenyl) acetate, benzyl bis (4-hydroxyphenyl) acetate Benzyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, isopropyl p-hydroxybenzoate, dibenzyl 4-hydroxyphthalate, dimethyl 4-hydroxyphthalate, ethyl 5-hydroxyisophthalate, 3,5-di-t -Butylsalicylic acid, stearyl gallate, lauryl gallate, octyl gallate, N, N'-diphenylthiourea, N, N'-di (m-chlorophenyl) thiourea, N- (p-toluenesulfonyl) -N ' -(3-p-butoxyphenyl) urea, N- (p-toluenesulfonyl) -N '-(p- Toxiphenyl) urea, N- (p-toluenesulfonyl) -N′-phenylurea, 2-hydroxy-3-naphthoic acid, 2-hydroxy-1-naphthoic acid, 1-hydroxy-2-naphthoic acid, etc. It can be used together in the developer composition.

(Sensitizer)
In the heat-sensitive recording material of the present invention, a sensitizer can be contained in the heat-sensitive coloring layer, if necessary. There are no particular restrictions on the sensitizers that can be used, but examples of sensitizers generally used for heat-sensitive recording materials include fatty acid amides such as stearamide and palmitic acid amide; Phenoxyethane, 1,2-bis (4-methylphenoxy) ethane, 1,2-bis (3-methylphenoxy) ethane, 1,2-bis (phenoxymethyl) benzene, 1,3-bis (phenoxymethyl) benzene 1,4-bis (phenoxymethyl) benzene, 1,2-bis (3-methylphenoxymethyl) benzene, 1,3-bis (3-methylphenoxymethyl) benzene, 1,4-bis (3-methylphenoxy) Methyl) benzene, 1,2-bis (4-methylphenoxymethyl) benzene, 1,3-bis (4-methylphenoxymethyl) benzene, 1,4-bis (4-methylphenoxymethyl) benzene 2-benzyloxynaphthalene, dibenzyl oxalate, di (4-methylbenzyl) oxalate, di (4-chlorobenzyl) oxalate, 4-acetylbenzyl, N-phenyltoluenesulfonamide, naphthyl toluenesulfonate, p -Benzylbiphenyl, m-terphenyl, 4,4'-dipropoxydiphenylsulfone, 4,4'-diisopropoxydiphenylsulfone, 4,4'-diallyloxydiphenylsulfone, 2,4'-dipropoxydiphenylsulfone, Examples include 2,4′-diisopropoxydiphenyl sulfone, 2,4′-diallyloxydiphenyl sulfone, benzyl p-benzyloxybenzoate, and benzyl terephthalate. These can be used alone or in combination of two or more.

(Image stabilizer)
In the heat-sensitive recording material of the present invention, an image stabilizer can be further contained in the heat-sensitive coloring layer. The image stabilizer used is not particularly limited, and examples thereof include 4-benzyloxy-4 ′-(2-methylglycidyloxy) -diphenylsulfone, 4,4′-diglycidyloxydiphenylsulfone, 4,4′-butylidenebis ( 3-methyl-6-tert-butylphenol), 2,2′-di-tert-butyl-5,5′-dimethyl-4,4′-sulfonyldiphenol, 1,1,3-tris (2-methyl- 4-hydroxy-5-t-butylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-cyclohexylphenyl) butane, compounds having a polyester structure such as polyhydroxybenzoic acid, urea urethane Examples thereof include a substance having a urethane structure such as a substance having a polyether structure such as poly (phenylsulfone) ether. These image stabilizers can be used alone or in combination of two or more.

(Fillers, other additives)
In the heat-sensitive recording material of the present invention, a filler can be contained in the heat-sensitive coloring layer as required. Examples of the filler used include inorganic fillers such as silica, calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, clay, talc, titanium oxide, aluminum hydroxide, zinc oxide, zinc hydroxide, barium sulfate, and surface-treated silica. And polystyrene microballs, nylon powder, urea-formalin resin filler, silicone resin particles, cellulose powder, styrene / methacrylic acid copolymer particles, vinylidene chloride resin particles, styrene / acrylic copolymer particles, plastic spherical hollow particles, etc. And organic fillers. These fillers can be used individually by 1 type, or can also be used in combination of 2 or more type.

  In the heat-sensitive recording material of the present invention, other additives can be contained in the heat-sensitive color developing layer as necessary. Examples of the additive to be contained include lubricants such as stearic acid ester wax, polyethylene wax and zinc stearate, benzophenone-based ultraviolet absorbers such as 2-hydroxy-4-benzyloxybenzophenone, benzotriazole, and 2- (2 ′ Examples thereof include triazole-based ultraviolet absorbers such as -hydroxy-5'-methylphenyl) benzotriazole, water-proofing agents such as glyoxal, dispersants, antifoaming agents, antioxidants, and fluorescent dyes.

(Manufacture of thermal recording materials)
There is no particular limitation on the method for producing the heat-sensitive recording material of the present invention, for example, a coloring substance, a developer, and a sensitizer, an image stabilizer, and other components to be added as necessary, together with an appropriate binder, It can be produced by dispersing in a medium such as an aqueous medium to prepare a coating solution for the thermosensitive coloring layer, coating the coating solution on a support, and drying. A dispersion containing a color former, a developer, and a sensitizer is prepared separately for each of a dispersion containing a color former, a dispersion containing a developer, and a dispersion containing a sensitizer. It is preferable to prepare by mixing these dispersions. In each dispersion liquid, it is desirable that the color developing substance, the color developing substance, and the sensitizer are dispersed in fine particles. Therefore, it is preferable to use a sand mill, a ball mill, or the like for the preparation of these dispersion liquids.

<Binder>
There are no particular limitations on the binder used, for example, cellulose derivatives such as hydroxyethylcellulose, methylcellulose, methoxycellulose, ethylcellulose, carboxymethylcellulose; polyvinyl alcohol, carboxy-modified polyvinyl alcohol, sulfone-modified polyvinyl alcohol, silicone-modified polyvinyl alcohol, amide-modified Polyvinyl alcohol cheeks such as polyvinyl alcohol; natural polymers such as gelatin, casein, starch, alginic acid; polyacrylic acid, polyacrylic acid ester, polyvinyl acetate, polymethacrylic acid ester, vinyl chloride / vinyl acetate copolymer, ethylene / Vinyl acetate copolymer, vinyl acetate / acrylic acid ester copolymer, polyacrylamide, acrylamide / acrylic acid ester copolymer , Acrylamide / acrylic acid ester / methacrylic acid terpolymer, isobutylene / maleic anhydride copolymer, styrene / acrylic acid ester copolymer, styrene / butadiene copolymer, styrene / butadiene / acrylic copolymer, Styrene / maleic anhydride copolymer, methyl vinyl ether / maleic anhydride copolymer, carboxy-modified polyethylene, polyvinyl alcohol / acrylamide block copolymer, polyvinyl pyrrolidone, melamine-formaldehyde resin, urea-formaldehyde resin, polyurethane, polyamide resin, A petroleum resin, a terpene resin, etc. can be mentioned. These binders can be used individually by 1 type, or can also be used in combination of 2 or more type.

(Support, undercoat layer, backcoat layer)
The support used for the heat-sensitive recording material of the present invention is not particularly limited, and examples thereof include paper such as neutral paper and acid paper, synthetic paper, recycled paper using waste paper pulp, film, nonwoven fabric, woven fabric, and the like. be able to.
In the heat-sensitive recording material of the present invention, on the support, silica, calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, clay, talc, titanium oxide, aluminum hydroxide, zinc oxide, zinc hydroxide, barium sulfate, Surface-treated inorganic fillers such as silica, polystyrene microballs, nylon powder, urea-formalin resin filler, silicone resin particles, cellulose powder, styrene / methacrylic acid copolymer particles, vinylidene chloride resin particles, styrene / acrylic copolymer It is preferable to provide an undercoat layer or a backcoat layer containing organic fillers such as polymer particles and plastic spherical hollow fine particles. By providing an undercoat layer or a backcoat layer, it can act as a heat insulating layer, and can improve sensitivity by efficiently using thermal energy from a thermal head or the like. In particular, an undercoat layer or a backcoat layer containing plastic spherical hollow fine particles can be suitably used because it can effectively improve thermal sensitivity.

In addition, the plastic spherical hollow fine particles are fine hollow particles having a thermoplastic resin as a shell, containing air or other gas inside and already foamed, and an average particle size of about 0.2 to 20 μm. belongs to. When the average particle diameter (particle outer diameter) is smaller than 0.2 μm, there are production problems such as difficult to obtain an arbitrary hollow ratio, which is difficult in terms of cost. Since the surface smoothness after coating and drying is lowered, the adhesion with the thermal head is lowered, and the effect of improving the thermal sensitivity is lowered. Therefore, it is preferable that the particles have a particle size in the above range and have little variation in particle size. Further, the plastic spherical hollow particles preferably have a hollow ratio of 40% or more, more preferably 90% or more, considering the heat insulating effect. Those having a low hollowness have insufficient heat insulation effect, so that heat energy from the thermal head is released to the outside of the heat-sensitive recording material through the support, resulting in poor heat sensitivity improvement effect. The “hollow ratio” referred to here is the ratio of the outer diameter to the inner diameter of the hollow fine particles, and is expressed below.
Hollow ratio (%) = [(inner diameter of hollow fine particles) / (outer diameter of hollow fine particles)] × 100
As described above, the plastic spherical hollow fine particles have a thermoplastic resin as a shell. Examples of the resin include polystyrene, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyacrylate, polyacrylonitrile, and polybutadiene. Or those copolymer resins etc. are mentioned. Among these, a copolymer resin mainly composed of vinylidene chloride and acrylonitrile is particularly preferable.

  There are no particular limitations on the binder used for the undercoat layer and the backcoat layer, for example, cellulose derivatives such as hydroxyethyl cellulose, methyl cellulose, methoxy cellulose, ethyl cellulose, carboxymethyl cellulose; polyvinyl alcohol, carboxy-modified polyvinyl alcohol, sulfone-modified polyvinyl alcohol, Polyvinyl alcohols such as silicone-modified polyvinyl alcohol and amide-modified polyvinyl alcohol; natural polymers such as gelatin, casein, starch and alginic acid; polyacrylic acid, polyacrylic acid ester, polyvinyl acetate, polymethacrylic acid ester, vinyl chloride / Vinyl acetate copolymer, ethylene / vinyl acetate copolymer, vinyl acetate / acrylate copolymer, polyacrylamide, acrylic Mido / acrylic acid ester copolymer, acrylamide / acrylic acid ester / methacrylic acid terpolymer, isobutylene / maleic anhydride copolymer, styrene / acrylic acid ester copolymer, styrene / butadiene copolymer, styrene / Butadiene / acrylic copolymer, styrene / maleic anhydride copolymer, methyl vinyl ether / maleic anhydride copolymer, carboxy-modified polyethylene, polyvinyl alcohol / acrylamide block copolymer, polyvinyl pyrrolidone, melamine-formaldehyde resin, urea Examples include formaldehyde resin, polyurethane, polyamide resin, petroleum resin, and terpene resin.

In the heat-sensitive recording material of the present invention, if necessary, a water-soluble resin such as a cellulose derivative or polyvinyl alcohol, a water-soluble emulsion such as a styrene-butadiene copolymer or a terpene resin, An overcoat layer can be formed by adding monomers or oligomers such as fillers, isocyanates, unsaturated compounds, and crosslinking agents to water-insoluble resins and those resins.
The heat-sensitive recording material of the present invention can be a multi-color heat-sensitive recording material in which color-forming substances having different color tones are formed in multiple layers as heat-sensitive color forming layers.

EXAMPLES Next, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited to these.
In the examples, the reactant composition and the compound composition were measured under the following conditions.
(Measurement conditions of gel permeation chromatography (GPC))
Chromatograph: “HLC-8020” manufactured by Tosoh Corporation
Column: Showa Denko Co., Ltd., “KF802”, Tosoh Co., Ltd. “TSK gel G3000H × L” connected in series.
Column temperature: 50 ° C
Mobile phase: Dimethylformamide Flow rate: 1.0 ml / min Detector: RI
(Measurement conditions of high performance liquid chromatography (HPLC))
Chromatograph: “SPD-10AVP” manufactured by Shimadzu Corporation
Column: “Shim-Pack CLC-ODS” manufactured by Shimadzu GL Co., Ltd.
φ6.0mm × 0.15m
Column temperature: 50 ° C
Mobile phase: 50% by mass acetonitrile water (0.3% by mass phosphoric acid)
Flow rate: 1.0 ml / min Detector: UV (254 nm)

In the examples and comparative examples, the effects of the produced heat-sensitive recording materials were evaluated by the following methods.
(1) Water resistance Using the thermal printing device [manufactured by Okura Electric Co., Ltd.] on the produced thermal recording material, color was developed at a printing voltage of 20 V and a pulse width of 3 ms, and the color density of the colored part (image part) was adjusted. It was measured using a reflection densitometer [manufactured by Macbeth, “RD-918”]. Next, after being immersed in water at 20 ° C. for 24 hours, it was air-dried at 20 ° C. and 65% RH for 2 hours, and the color density of the image area was measured.
Storage rate (%) = [(color density after test / color density before test)] × 100
(2) Humidity and heat resistance Using the thermal printing device [manufactured by Okura Electric Co., Ltd.], the produced thermosensitive recording material was developed with a printing voltage of 20 V and a pulse width of 3 ms, and the color density of the colored portion (image part) was determined. It was measured using a reflection densitometer [manufactured by Macbeth, “RD-918”]. Next, after being allowed to stand at 60 ° C. and a relative humidity of 80% for 24 hours, the color density of the image area was measured, and the storage rate was determined by the following formula.
Storage rate (%) = [(color density after test / color density before test)] × 100
(3) Heat resistance The color density of an uncolored portion (uncolored portion) of the produced thermosensitive recording material was measured using a reflection densitometer [Macbeth Co., Ltd., “RD-918”]. Next, after standing at 90 ° C. or 100 ° C. for 24 hours, the color density was measured.

Synthesis example 1
In a four-necked flask equipped with a stirrer, a reflux condenser, and a thermometer, 100 g of 4,4′-dihydroxydiphenylsulfone [manufactured by Nikka Chemical Co., Ltd., trade name “BPS-P (T)”] and 200 g of isopropanol are placed. 4,4′-Dihydroxydiphenyl sulfone was dissolved. Subsequently, 300 g of an aqueous solution in which 24 g of sodium hydroxide was dissolved was added and heated to 60 ° C., and then 50 g of 4,4′-bis (chloromethyl) -1,1′-biphenyl was added and heated under reflux for 3 hours. Stirred. Thereafter, 4 g of sodium hydroxide was added, and the mixture was further stirred for 2 hours. Subsequently, after cooling to 50 degreeC and diluting dilute hydrochloric acid aqueous solution and neutralizing, it heated again, and isopropanol was distilled off. The crystals were filtered under reduced pressure at 60 ° C., and the crystals were washed with 100 g of hot water at 60 ° C. 50 g of methanol and 250 g of water were added to the obtained crystals, heated under reflux for 1 hour, cooled to 40 ° C., and the crystals were isolated by filtration under reduced pressure. When dried, 98 g of a white reaction product was obtained.
The composition of this reaction product was measured by gel permeation chromatography [manufactured by Tosoh Corporation] and confirmed to be the following composition.

ｍ＝０：保持時間 ２８.６分：ピーク面積比（％) ３
ｍ＝１：保持時間 ２６.０分：ピーク面積比（％） ４２
ｍ＝２：保持時間 ２４.５分：ピーク面積比（％） ２２
ｍ＝３：保持時間 ２３.５分：ピーク面積比（％） ８
ｍ＝４：保持時間 ２２.７分：ピーク面積比（％） ７
ｍ＝５：保持時間 ２２.１分：ピーク面積比（％） ７
ｍ＝６：保持時間 ２１.６分：ピーク面積比（％） ６

m = 0: Retention time 28.6 minutes: Peak area ratio (%) 3
m = 1: Retention time 26.0 minutes: Peak area ratio (%) 42
m = 2: Retention time 24.5 minutes: Peak area ratio (%) 22
m = 3: Retention time 23.5 minutes: Peak area ratio (%) 8
m = 4: Retention time 22.7 minutes: Peak area ratio (%) 7
m = 5: Retention time 22.1 minutes: Peak area ratio (%) 7
m = 6: Retention time 21.6 minutes: Peak area ratio (%) 6

ＨＰＬＣによる上記一般式（２）で表されるジフェニルスルホン架橋型化合物（ｂ）の測定でｎ＝１のリテンションタイムは、９.２分、ｎ＝２のリテンションタイムは１５.３分であった。また、合成例１の反応生成物をＨＰＬＣで測定した結果、ジフェニルスルホン架橋型化合物（ｂ）の含有率は、４.５質量％であった。単離したジフェニルスルホン架橋型化合物（ｂ）を¹Ｈ−ＮＭＲ（使用溶媒：重水素化ジメチルスルホキシド）で測定し、５.２ｐｐｍに（−ＣＨ₂Ｏ−）のシングレットピークを、４.６ｐｐｍに（−ＣＨ₂ＯＨ）のシングレットピークを、６.７〜７.８ｐｐｍに（Ａｒｏｍａｔｉｃ ｒｉｎｇ−Ｈ）のピークを確認した。

The retention time of n = 1 was 9.2 minutes and the retention time of n = 2 was 15.3 minutes as determined by HPLC of the diphenylsulfone bridged compound (b) represented by the general formula (2). . Moreover, as a result of measuring the reaction product of the synthesis example 1 by HPLC, the content rate of the diphenyl sulfone bridge | crosslinking type compound (b) was 4.5 mass%. The isolated diphenylsulfone bridged compound (b) was measured by ¹ H-NMR (solvent: deuterated dimethyl sulfoxide), and the singlet peak of (—CH ₂ O—) was reduced to 4.6 ppm at 4.6 ppm. A singlet peak of (—CH ₂ OH) and a peak of (Aromatic ring-H) were confirmed at 6.7 to 7.8 ppm.

Example 1 (washing with methanol)
To a four-necked flask equipped with a stirrer, a reflux condenser, and a thermometer, 50 g of a dried product of crystals obtained in Synthesis Example 1 and 250 g of methanol were added, and the mixture was stirred for 3 hours in a heated reflux state. After cooling to 35 ° C., the crystals were filtered under reduced pressure, and the crystals were washed with 50 g of methanol. This was dried to obtain 45 g of white crystals. The content of the diphenylsulfone crosslinking compound (b) represented by the general formula (2) in the crystal was 1.2% by mass.

Example 2 (washing with isopropanol)
To a four-necked flask equipped with a stirrer, a reflux condenser, and a thermometer, 50 g of the dried crystal product obtained in Synthesis Example 1 and 250 g of isopropanol were added, and the mixture was stirred for 3 hours while heating and refluxing. After cooling to 35 ° C., the crystals were filtered under reduced pressure, and the crystals were washed with 50 g of isopropanol. This was dried to obtain 45 g of white crystals. The content of the diphenylsulfone crosslinking compound (b) represented by the general formula (2) in the crystal was 2.5% by mass.

Example 3
By dispersing 10 parts by weight of 3-dibutylamino-6-methyl-7-anilinofluorane, 10 parts by weight of a 10% by weight aqueous polyvinyl alcohol solution and 30 parts by weight of water using a sand mill for 4 hours, A coloring substance dispersion (liquid A) was prepared. A developer dispersion liquid (10 parts by weight of white crystals obtained in Example 1, 10 parts by weight of a 10% by weight aqueous polyvinyl alcohol solution and 30 parts by weight of water was finely pulverized using a sand mill for 3 hours. B liquid) was prepared. Silica gel dispersion was achieved by finely pulverizing and dispersing 10 parts by mass of silica gel [manufactured by Mizusawa Chemical Co., Ltd., “P527”], 10 parts by mass of a 10% by weight polyvinyl alcohol aqueous solution and 30 parts by mass of water using a sand mill. A liquid (liquid C) was prepared. A zinc stearate dispersion (liquid D) was prepared by pulverizing and dispersing 10 parts by weight of zinc stearate, 10 parts by weight of a 10% by weight aqueous polyvinyl alcohol solution and 30 parts by weight of water using a sand mill for 3 hours. . Non-foaming plastic micro hollow particles (solid content 24% by mass, average particle size 3 μm, hollowness 90%) 40 parts by mass, styrene / butadiene copolymer latex [manufactured by Nippon Zeon Co., Ltd., “Nipol (registered trademark) LX438C ]] A resin liquid (liquid E) was prepared by stirring and mixing 10 parts by mass and 50 parts by mass of water using a disper.
Next, 5 parts by mass of A liquid, 20 parts by mass of B liquid, 20 parts by mass of C liquid, and 2.5 parts by mass of D liquid were stirred and mixed using a disper to prepare a coating solution for a coloring layer. Moreover, 5 mass parts of C liquid and 10 mass parts of E liquid were stirred and mixed using the disper, and the coating liquid of the undercoat layer was prepared.
The high-quality paper having a basis weight 60 g / m ^2, by coating a coating solution for undercoat layer so as to have a dry coating amount of the 3 g / m ^2, to obtain an undercoat coated paper and dried. On this undercoat layer, a color layer coating solution is applied so that the dry coating amount is 5 g / m ² , dried, and calendered at a pressure of 0.98 MPa to produce the thermosensitive recording material of the present invention. And evaluated.

Example 4
Example 3 except that a developer dispersion (liquid B) was prepared using 10 parts by weight of the white crystals obtained in Example 2 instead of 10 parts by weight of the white crystals obtained in Example 1. Similarly, a heat-sensitive recording material was produced and evaluated.

Comparative Example 1
Example 3 except that the developer dispersion (liquid B) was prepared using 10 parts by mass of the reaction product obtained in Synthesis Example 1 instead of 10 parts by mass of the white crystals obtained in Example 1. In the same manner as above, a heat-sensitive recording material was produced and evaluated.
The evaluation results of the heat-sensitive recording materials of Examples 3 and 4 and Comparative Example 1 are shown in Table 1.

The polycondensation reaction product in the presence of water contains the diphenylsulfone crosslinking compound (b), but the content of the diphenylsulfone crosslinking compound (b) is lowered by washing with methanol, ethanol or isopropanol. In particular, the cleaning effect with methanol was good.
Further, as shown in Table 1, the water resistance of the image areas of Example 3 (compound (b) content: 1.5 mass%) and Example 4 (compound (b) content: 2.4 mass%). In addition, since the heat and moisture resistance and the heat resistance of the non-colored product are both good and no difference in effect is recognized between them, if the content of the diphenylsulfone cross-linking compound (b) is 3% by mass or less, It was confirmed that the heat-sensitive recording material using the developer composition containing the diphenylsulfone crosslinking type compound (a) exhibits a certain water resistance and heat and moisture resistance. Such a developer composition is also excellent in storage stability of an uncolored portion (background). On the other hand, Comparative Example 1 (compound (b) content: 4.5 mass%) in which the content of the diphenylsulfone cross-linking compound (b) in the developer composition exceeds 3 mass% is the water resistance of the image area. Inferior in heat resistance and wet heat resistance, a remarkable difference is recognized as compared with the effects of Examples 3 and 4.

  Since the heat-sensitive recording material of the present invention is excellent in water resistance and moisture and heat resistance of the image area, even if it is used in an environment where moisture or wet heat is applied after printing, for example, a microwave heated food label, parking ticket, delivery label, etc. The recorded information can be held stably.

Claims (5)

A developer composition for thermal recording containing a diphenylsulfone crosslinkable compound (a) represented by the following general formula (1), wherein the diphenylsulfone crosslinkable compound (b) represented by the following general formula (2): ) Content of 3% by mass or less.

  A heat-sensitive recording material comprising a heat-sensitive color-developing composition according to claim 1 and a heat-sensitive color-developing layer containing a colorless or light-colored leuco dye as a color-developing substance on a support. A method for producing a developer composition for thermal recording, comprising a crystal containing a diphenylsulfone crosslinking compound (a) represented by the following general formula (1):
By heating a reaction product obtained by reacting dihydroxydiphenyl sulfone and 4,4′-bis (halomethyl) biphenyl in a solvent in a branched or straight chain alcohol having 1 to 4 carbon atoms, the following general formula A method for producing a developer composition for thermal recording, comprising the step of obtaining the crystal having a content of the diphenylsulfone cross-linking compound (b) represented by (2) of 3% by mass or less.

The developer composition for thermal recording according to claim 3, wherein the amount of the branched or straight chain alcohol having 1 to 4 carbon atoms is 3 to 10 times the mass of the reaction product. Manufacturing method. Obtaining a developer composition for thermal recording by the production method according to claim 3 or 4,
  A step of providing a heat-sensitive color developing layer containing the heat-sensitive recording developer composition and a colorless or light leuco dye as a color developing material on a support;
  A method for producing a heat-sensitive recording material.